The present invention relates to a looper and a cutter drive mechanism for sewing machine, and more particularly to a looper and a cutter drive mechanism for sewing machine which can perform lock stitching and over-edge stitching integrally and further can perform such stitchings by changing over an operation which performs the over-edge stitching in the lock stitching by cutting a fabric edge and an operation which performs the lock stitching without cutting the fabric edge.
Conventionally, as the most fundamental stitch formed by a sewing machine among stitches formed by joining a plurality of fabrics or the like, a lock stitching is known. In the lock stitching, when an upper thread which is made to pass through a needle is made to penetrate the fabric along with the vertical movement of the needle, by intercepting the upper thread with a loop-taker point of a rotary hook which accommodates a lower thread so that the upper thread and the lower thread are crossed with each other to form the lock stitching whereby a plurality of fabrics are securely joined along the stitch.
On the other hand, as the stitching which can prevent unraveling of peripheral portions of the fabrics or the like which are liable to be disintegrated, an over-edge stitching is known. In the over-edge stitching, depending on the number of threads for forming the stitch and the number of needles which perform an approximately vertical movement relative to a fabric surface, there have been known a single-needle two-thread over-edge stitching (U.S.A. Stitch standard: Stitch type 503), a single-needle three-thread over-edge stitching (U.S.A. Stitch standard: Stitch type 504), and further a two-needle five-thread stitching (U.S.A. Stitch standard: Stitch type 516) which combines a chain stitching and the over-edge stitching and is usually called an interlock.
However, in such an over-edge stitching, to form stitches, a thread is intercepted from side by two hook-shaped needles called loopers or looper threads which move horizontally are intercepted by needles. In this manner, since the looper threads do not cross in the direction perpendicular to the fabric surface with respect to the needle thread, it is impossible to securely join the fabrics as in the case of the lockstitching. That is, there arises a so-called xe2x80x9claughingxe2x80x9d phenomenon in which when two fabrics joined by the over-edge stitching are opened, the stitching threads are exposed outside. Accordingly, in performing the over-edging after joining a plurality of fabrics, it is necessary to form the stitch (U.S.A. Stitch standard: Stitch type 517) by performing the lockstitch.
In such a stitch (U.S.A. Stitch standard: Stitch type 517), although it is desirable that the lockstitch portion and the over-edge portion are disposed as close as possible to each other, the lockstitch requires a rotary hook to accommodate a lower thread below the needle which performs the vertical movement, while the over-edge stitching requires loopers which move to cross a locus of the vertical movement of a needle which is provided separately from the needle of the lockstitching and hence, there naturally exists a limit with respect to the respective positions of the lockstitch portion and the over-edge stitching portion. In view of the above, sewing machines which can be used for both of the lockstitching and the over-edge stitching have been proposed in Japanese Patent Publication 15268/1981, Japanese Patent Publication 25145/1985, Japanese Patent Publication 25396/1986 and the like. However, all of the sewing machines disclosed in these publications are sewing machines which selectively use one of these functions and it has been impossible to perform the lockstitching and the over-edge stitching simultaneously in a state that the lockstitching and the over-edge stitching are disposed close to each other.
On the other hand, methods in which the lockstitching and the over-edge stitching can be performed simultaneously have been proposed as disclosed in Japanese Laid-open Patent Publication 113490/1980, Japanese Laid-open Patent Publication 136085/1980, Japanese Laid-open Patent Publication 146190/1980, Japanese Laid-open Patent Publication 122495/1988 and the like. However in these proposals, with respect to the over-edge stitching, since the loopers which cross the locus of the vertical movement of a needle and are provided separately from the lockstitching adopt the looper movement of the above-mentioned conventional over-edge stitching as their movement, the lockstitching requires a rotary hook to accommodate the lower thread below the needle which performs the vertical movement and the over-edge stitching requires the loopers which performs their movement such that the movement crosses the locus of the vertical movement of the needle provided separately from the lockstitching. Accordingly, there naturally exits a limit with respect to the positions of the over-edge stitching and the lockstitching and it has been difficult to perform the lockstitching and the over-edge stitching simultaneously in a state that the lockstitching and the over-edge stitching are disposed close to each other in terms of the mechanism of the sewing machine.
Further, a lockstitching/over-edge stitching attachment (manufactured by TOYO SEIKI KOGYO KABUSHIKIGAISHA, product name xe2x80x9cRUBYLOCKxe2x80x9d) which simultaneously performs the lockstitching and the over-edge stitching has been proposed (Japanese Patent Publication 2541601). As shown in FIG. 27, this attachment is used in a form that it is fixedly mounted on a fabric presser rod 1001. A drive arm 1003a of a crank 1003 journalled in an attachment frame 1002 is driven by a needle rod (not shown in the drawing) which carries a needle 1011. A driven arm 1003b rocks an upper looper drive plate 1005 supported on the attachment frame 1002 by way of a drive connection link 1004. Due to the rocking of this upper looper drive plate 1005, an upper looper 1007 supported on the attachment frame 1002 by way of an upper looper drive link 1006 is rocked. On the other hand, due to this rocking of the upper looper drive plate 1005, a pin 1005a mounted on the upper looper drive plate 1005 in a protruding manner slides in and along a groove 1008a formed in a lower looper drive plate 1008 journalled in the attachment frame 1002 and rocks this lower looper drive plate 1008. Due to this rocking of the lower looper drive plate 1008, a lower looper 1010 journalled in the attachment frame 1002 is rocked by way of a lower looper drive link 1009. In such an attachment structure, since the upper looper 1007 must intersect the needle 1011 on the upper surface of a fabric (not shown in the drawing), the upper looper 1007 is inclined in a left upward direction as seen from the fabric feeding and advancing direction. Further, since the lower looper 1010 must intersect the needle 1011 on the lower surface of the fabric, the lower looper 1010 is inclined in the left downward direction as seen from the fabric feeding and advancing direction. Further, the upper and lower loopers 1007, 1010 are inclined such that the upper and lower loopers 1007, 1010 interloop each other at a side of the fabric end of the fabric.
In the drawing, numeral 1014 indicates a needle stitching portion of the needle 1011, numeral 1012 indicates a thread tension equipment and numeral 1013 indicates a looper thread take-up driven by the lower looper drive plate 1008.
In the attachment having such a constitution, when the needle bar performs the upward and downward movement, the lockstitching is formed by the needle thread (not shown in the drawing) which passes through the needle 1011 and the lower thread (not shown in the drawing) accommodated in a rotary hook (not shown in the drawing). Simultaneously, the drive arm 1003a of the crank 1003 is driven by the needle bar and the driven arm 1003b rocks the upper looper drive plate 1005 by way of the drive connection link 1004. Due to this rocking of the upper looper drive plate 1005, the upper looper 1007 is rocked by way of the upper looper drive link 1006. Due to this rocking of the upper looper drive plate 1005, the pin 1005a which is mounted on the upper looper drive plate 1005 in a protruding manner slides in and along the groove 1008a formed in the lower looper drive plate 1008 so as to rock the lower looper drive plate 1008. Due to this rocking of the lower looper drive plate 1008, the lower looper 1010 is rocked by way of the lower looper drive link 1009 so that the over-edge stitching is formed by the upper looper thread and the lower looper thread (not shown in the drawing) which respectively pass through the upper looper 1007 and the lower looper 1010.
However, in such an attachment, since the upper and lower loopers 1007, 1010 are inclined, a high machining technique is required in manufacturing and a technique which maintains accuracy in assembling is also required. Further, since this type of lockstitch sewing machine is used by a general household or a tailor as a user, an operation to exchange a fabric presser of the attachment and to fixedly secure the fabric presser to the fabric presser bar becomes extremely cumbersome and an operation to adjust the positional relationship of the upper looper 1007 and the lower looper 1010 relative to the needle after fixedly securing the attachment becomes also extremely cumbersome. This attachment also suffers from a serious drawback that the over-edge stitching operation must be performed after preliminarily cutting the edge of the fabric to be stitched by the over-edge stitching using scissors.
Accordingly, inventors of the present application have proposed a single-needle four-thread lockstitch/over-edge stitch structure and a method for forming such stitching which have both of the lockstitching function and the over-edge stitching function and can form such a stitch structure at a time using a sewing machine (Japanese Patent Publication 2672097). Users of the lockstitch sewing machines have been strongly desiring the research and the development of a lockstitch sewing machine which can realize the single-needle four-thread lockstitch/over-edge stitch structure and a method for forming such a stitch structure disclosed in the above proposal.
Further, all of the single-needle two-thread over-edge stitching (U.S.A. Stitch standard: Stitch type 503), the single-needle three-thread over-edge stitching (U.S.A. Stitch standard: Stitch type 504), the two-needle five-thread over-edge stitching (U.S.A. Stitch standard: Stitch type 516) and the like employed for forming stitches of over-edge stitching perform an over-edge stitching by cutting a fabric edge with cutters consisting of an upper cutter which performs the upward and downward movement and a lower cutter which is cooperatively operated with the upper cutter.
Here, it is considered that the over-edge stitching can be performed easily even in the lockstiching if a zigzag stitching is performed after cutting the fabric edge in a zigzag pattern. Based on such a consideration, a sewing machine which adds a cutter cutting function to the lockstitching has been proposed in Japanese Utility Model Laid-open Application 90056/1982, 90057/1982, Japanese Patent Publication 31950/1983 and the like.
Here, in general, in addition to a request that the lockstitch sewing machine must be manufactured in a compact form, it is desirable that the lockstitch portion and the cutter cutting mechanism portion are disposed as close as possible to each other. However, since the lockstitching requires a rotary hook which accommodates a lower thread below a needle which performs the upward and downward movement, there naturally exists a limit in incorporating the cutter cutting mechanism portion into an existing structural space of the lockstitch sewing machine. In this manner, it has been conventionally difficult to physically realize a lockstitch sewing machine which can perform the lockstitching and the fabric-edge cutting simultaneously and to commertialize such a lockstitch sewing machine due to the mechanism of the sewing machine.
The present invention has been made to overcome these conventional drawbacks and it is an object of the present invention to provide a looper drive mechanism of a sewing machine which has both of lockstitching function and over-edge stitching function and can perform them at a time using a single sewing machine.
Further, it is another object of the present invention to provide a cutter drive mechanism of a sewing machine which can incorporate a cutter cutting mechanism portion into an existing structural space of the sewing machine and can change over an operation to perform the over-edge stitching in the lockstitching by cutting a fabric edge and an operation to perform the lockstitching without cutting the fabric edge.
To achieve such an object, in a looper drive mechanism for sewing machine in which using an upper thread which is made to pass through a needle which performs an upward and downward movement drawing a trace vertically relative to a throat plate and a lower thread accommodated in a rotary hook, the upper thread which is made to pass through the needle performing the reciprocating movement in the vertical direction and passing through a work mounted on the throat plate every one stitch feed of the work is, at the time of elevating the upper thread from a lowermost position of the needle, intercepted by a loop-taker point of the rotary hook which accommodates the lower thread below the throat plate and performs the rotary movement so as to make the upper thread and the lower thread interlace each other thus forming a lockstitch portion made of a stitch parallel to a surface of the work and a stitch perpendicular to the surface of the work, and an over-edge stitch portion is formed by an upper looper thread and a lower looper thread which are respectively made to pass through an upper looper which performs a reciprocating movement drawing a substantially arcuate trace extending above and below the throat plate and intersects the trace of the needle above the throat plate and a lower looper which draws a substantially arcuate trace below the throat plate and intersects the trace of the needle and the trace of the upper looper respectively, the looper drive mechanism for sewing machine further includes a looper drive portion having a constitution in which the upper looper and the lower looper are respectively disposed below the throat plate, respective loop-taker points thereof are arranged in the same direction such that the loop-taker points pass a front side of the needle as seen in the stitching direction, the upper looper and the lower looper are driven such that the upper looper and the lower looper perform movements having traces on planes substantially parallel to each other, the upper looper thread which is made to pass through the upper looper which performs the reciprocating movement drawing the arcuate trace which intersects the trace of the needle above the throat plate and passes through the throat plate is intercepted by the needle descending from an uppermost position when the upper looper is descended from an uppermost position, the lower looper thread which is made to pass through the lower looper which performs the reciprocating movement drawing the trace which intersects the trace of the needle and the trace of the upper looper below the throat plate is intercepted by the descending needle below the throat plate when the lower looper is moved from one end to the other end of the trace, and the lower looper thread is intercepted by the upper looper elevating from the lowermost position when the lower looper is moved to the other end, whereby the upper looper thread and the lower looper thread are interlooped each other at the edge portion of the work and, at the same time, the upper looper thread is interlooped with the lockstitch portion through the upper surface of the work, and the lower looper thread is interlooped with the lockstitch portion through the lower surface of the work thus forming the over-edge stitch portion.
The looper drive portion includes a crank which is mounted on a looper drive shaft driven by a lower drive shaft, a lower looper drive link which is connected to the crank, a lower looper mounting arm for carrying the lower looper which is connected to the lower looper drive link and journalled in a frame, an upper looper mounting arm for carrying the upper looper which is journalled in the frame, and an upper looper drive link which connects the lower looper drive link and the upper looper mounting arm.
The looper drive mechanism of sewing machine includes a clutch which forms the lockstitch portion and the over-edge portion by transmitting power from the lower shaft to the looper drive shaft at the time of forming the over-edge portion, and forms the lockstitch portion by shunting the upper looper at the lowermost position and interrupting the transmission of power from the lower shaft to the looper drive shaft at the time of forming the lockstich portion.
In such a looper drive mechanism of sewing machine, the upper looper and the lower looper are respectively disposed below the throat plate, respective loop-taker points thereof are arranged in the same direction such that the loop-taker points pass a frontal side of the needle as seen in the stitching direction, the upper looper and the lower looper are driven such that the upper looper and the lower looper perform movements having traces on planes substantially parallel to each other, whereby the looper drive mechanism has both of the lockstitching function and the over-edge stitching function and they can be performed simultaneously at a time by a single sewing machine.
Further, the clutch can be changed over such that the clutch forms the lockstitch portion and the over-edge portion by transmitting power from the lower shaft to the looper drive shaft at the time of forming the over-edge portion, and forms the lockstitch portion by shunting the upper looper at the lowermost position and interrupting the transmission of power from the lower shaft to the looper drive shaft at the time of forming the lockstich portion.
Still further, a cutter drive mechanism of sewing machine to achieve the above-mentioned object is a cutter drive mechanism of sewing machine for cutting a fabric edge by an upper cutter which performs upward and downward movement by way of a motion transfer mechanism which is operated with a rotary shaft of the sewing machine in an interlocking manner and a lower cutter which is cooperatively operated with the upper cutter, wherein the cutter drive mechanism of sewing machine includes a cutter drive portion pivotally mounted on a frame and slidably guides the upper cutter, and the motion transfer mechanism is connected to the upper cutter such that by way of a clutch which allows the transmission of power to the upper cutter when the cutter operation of the cutter drive portion is performed and interrupts the transmission of power to the upper cutter by pivotally moving the cutter drive portion to a shunting position at the time of not operating the cutters.
The motion transfer mechanism includes a first quadric crank chain which connects an upper shaft constituted by the rotary shaft and the frame and a second quadric crank chain which uses one link of the first quadric crank chain and a link joint of the frame and adopts a drive portion of the clutch as the other one link.
The clutch includes a pin which is formed on the other one link as a drive portion and an elongated groove formed in the upper cutter for allowing the pin to be fitted thereinto as a driven portion.
The lower cutter is slidably mounted on the cutter drive portion and the lower cutter includes a locating locking-portion which positions the cutter drive portion at a locating recessed-portion of a throat plate relative to a needle stitching position at the time of operating the cutters.
The locating recessed-position of the throat plate is constituted position-adjustably in the rightward and leftward direction such that the stitch width can be changed relative to the needle stitching position.
The lower cutter is slidably mounted on the cutter drive portion and the cutter drive mechanism of sewing machine further includes a cutter-side pressure spring member which biases the upper cutter to the lower cutter.
The lower cutter is slidably mounted on the cutter drive portion and the cutter drive mechanism of sewing machine further includes a locating spring member which biases the locating locking-portion to the locating recessed-portion of the throat plate at the time of performing the cutting operation.
The lower cutter is slidably mounted on the cutter drive portion and the cutter drive mechanism of sewing machine further includes a locating eccentric cam which fits the locating locking-portion into the locating recessed-portion of the throat plate at the time of performing the cutting operation.
The upper cutter is replaceably mounted on the cutter drive portion.
In the cutting drive mechanism having such a constitution, the rotational movement of the rotary shaft of the sewing machine is transferred to the upward and downward movement by way of the motion transfer mechanism which is operated in an interlocking manner with the rotary shaft and the fabric edge is cut by the upper cutter and the lower cutter which cooperates with the upper cutter due to this upward and downward movement. Here, the upper cutter is slidably guided by the cutter drive portion pivotally supported on the frame. The motion transfer mechanism is connected to the upper cutter by way of the clutch. The clutch transmits power to the upper cutter when the cutter operation of the cutter drive portion is performed and interrupts the transmission of the power to the upper cutter by pivotally moving the cutter drive portion to the shunting position when the cutter operation of the cutter drive portion is not performed.
Further, the lower cutter of the cutter drive mechanism of the sewing machine of the present invention is slidably mounted on the cutter drive portion and includes a locating locking-portion which locates the cutter drive portion at the locating recessed-portion of the throat plate relative to the needle stitching position at the time of operating the cutters, and the cutter drive portion includes a locating lever which fits the locating locking-portion into the locating recessed-portion of the throat plate at the time of performing the cutter operation.
In the cutting drive mechanism of the sewing machine having such a constitution, the rotational movement of the rotary shaft of the sewing machine is transferred to the upward and downward movement by way of the motion transfer mechanism which is operated in an interlocking manner with the rotary shaft and the fabric edge is cut by the upper cutter and the lower cutter which cooperates with the upper cutter due to this upward and downward movement. Here, the upper cutter is slidably guided by the cutter drive portion pivotally supported on the frame. The motion transfer mechanism is connected to the upper cutter by way of the clutch.
The clutch transmits power to the upper cutter when the cutter operation of the cutter drive portion is performed and interrupts the transmission of the power to the upper cutter by pivotally moving the cutter drive portion to the shunting position when the cutter operation of the cutter drive portion is not performed. Here, with the use of the locating lever of the cutter drive portion, after the locating locking-portion of the lower cutter is removed from the locating recessed-portion of the throat plate, the cutter drive mechanism can be directly pivotally moved to the shunting position.